Viruses 2011, 3, 561-585; doi:10.3390/v3050561 OPEN ACCESS viruses ISSN 1999-4915 www.mdpi.com/journal/viruses Review Foamy Virus Biology and Its Application for Vector Development Dirk Lindemann 1,2,* and Axel Rethwilm 3 1 Institut für Virologie, Medizinische Fakultät ―Carl Gustav Carus‖, Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany 2 DFG-Center for Regenerative Therapies Dresden (CRTD)—Cluster of Excellence, Biotechnology Center, Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany 3 Institut für Virologie und Immunbiologie, Universität Würzburg, 97078 Würzburg, Germany; E-Mail:
[email protected] * Author to whom correspondence should be addressed; E-Mail:
[email protected]; Tel.: +49-351458-6210; Fax: +49-351-458-6310. Received: 7 March 2011; in revised form: 21 April 2011 / Accepted: 23 April 2011 / Published: 11 May 2011 Abstract: Spuma- or foamy viruses (FV), endemic in most non-human primates, cats, cattle and horses, comprise a special type of retrovirus that has developed a replication strategy combining features of both retroviruses and hepadnaviruses. Unique features of FVs include an apparent apathogenicity in natural hosts as well as zoonotically infected humans, a reverse transcription of the packaged viral RNA genome late during viral replication resulting in an infectious DNA genome in released FV particles and a special particle release strategy depending capsid and glycoprotein coexpression and specific interaction between both components. In addition, particular features with respect to the integration profile into the host genomic DNA discriminate FV from orthoretroviruses. It appears that some inherent properties of FV vectors set them favorably apart from orthoretroviral vectors and ask for additional basic research on the viruses as well as on the application in Gene Therapy.